No one knows the real "trick" to getting pin codes... but many folks who register at the Disney site, and then "plan" vacations (without actually booking them) will see a pin code via email a few weeks later. Like PP mentioned, there are currently great offers out there for travel into mid-August.
A bounceback is an offer that you receive WHILE you are at Disney. It is typically a room discount offer (but could also be for a package) that MUST be booked before you check out of your hotel.
Welcome to the Dis, and feel free to ask lots of questions!